The eighteenth law is Precision, which states: The interface will allow the users to perform a task exactly.

Human Factors

Users want to know that when they perform a task, it will be done accurately and the results will be correct.

Technology Considerations and Implications

Precision will go awry for three reasons:

  • There are errors in the underlying code.
  • The user and the computer have different expectations of the definition of a task or its outcome.
  • There are errors during the interaction, such as speech recognition errors that lessen precision.

The first item—errors in the underlying code—is not directly related to the interface; however, the second and third issues are related. They must be addressed during the design process to minimize their occurrence and the negative effect on precision.

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